JP2009048085A - Small-diameter objective optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-diameter objective optical system suitable for in vivo observation with a high numerical aperture by reducing the outer diameter and effectively correcting various aberrations. <P>SOLUTION: The invention provides a small-diameter objective optical system comprising, in order from an object plane a first lens group with positive refractive power, including at least one plano-convex lens whose convex surface faces an image plane; a second lens group with positive refractive power, including at least one concave lens; and a third lens group including a cemented lens whose cemented surface has negative refractive power. The focal length of the third lens group is longer than the focal length of the first lens group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an objective optical system used for applications such as elucidation of cell functions and imaging, and particularly relates to a small-diameter objective optical system suitable for observing animals such as mammals alive.

Conventionally, a dye or fluorescent marker is attached to a specific molecule, tissue, cell, etc., and this is observed with a fluorescence microscope or a confocal laser scanning microscope to observe the behavior of molecules in biological cells and tissues. Has been done.
The behavior of molecules in a living state of a mammal such as a mouse may be different from that of a cultured cell, and observation of living tissues and cells is performed while the individual is alive (in vivo). (For example, refer to Patent Document 1).
JP 2006-119300 A

  Microscopes such as conventional laser scanning confocal microscopes do not assume that various organs of small experimental animals such as rats and mice are observed in a living state (in vivo). When observing the inside of a living individual, since the outer diameter of the objective lens is large in a conventional microscope, it is necessary to open and observe the living body greatly. However, since the invasiveness is high when the living body is largely opened, long-term observation is impossible.

  The objective optical system of Patent Document 1 has a thin tip diameter but is still highly invasive when observing deep parts such as a mouse brain. In other words, in order to observe various organs of small experimental animals, it is necessary to incise the epidermis and muscle tissue, or to pierce the skull to expose the internal organs. Therefore, when observing an internal organ or the like, it is necessary to make a large incision or open a large hole in the epidermis or muscle tissue. In this case, observation is possible immediately after incision of the tissue or immediately after perforation. However, since the experimental small animal is seriously damaged, observation over time over a long period of time is difficult. Although a method of suturing after observation and incising again at the next observation can be considered, considering the damage given to the experimental small animal, there is a disadvantage that observation in a normal state becomes difficult as time passes.

  The present invention has been made in view of the above-described circumstances, and remains alive in mammalian cells including experimental small animals, biological tissues such as muscles, or various organs such as heart and liver, particularly brain tissues. It is an object of the present invention to provide an objective optical system that enables minimally invasive observation over a relatively long period of time.

In order to achieve the above object, the present invention provides the following means.
In the present invention, in order from the object surface side, a first lens unit having positive refractive power including at least one plano-convex lens having a convex surface directed toward the image surface side, and a second lens group having positive refractive power including at least one concave lens. , And a third lens group including a cemented lens having a negative refractive power, and a focal length of the third lens group is larger than a focal length of the first lens group. .

  According to the present invention, the first lens unit having a positive refractive power converts divergent light into divergent light that is substantially parallel light or nearly parallel light. Further, by including a plano-convex lens having a convex surface facing the image surface side, it is possible to reduce the spherical aberration and coma generated by the plano-convex lens close to the aplanatic condition.

  The second lens group having positive refractive power can expand the substantially parallel light beam from the first lens group or a divergent light beam close to the substantially parallel light beam into a substantially parallel light beam having a larger diameter.

  The third lens group corrects aberrations such as spherical aberration and coma aberration generated in the first and second lens groups, and chromatic aberration with a cemented surface having negative refractive power. Also, the height of the light beam can be increased by making the focal length of the third lens group larger than the focal length of the first lens group.

In the said invention, it is preferable to satisfy the following conditional expressions (1).
(1) 0.2 <(F ₁ × h ₃ ) / (F ₃ × h ₁ ) <0.3
Where F ₁ is the focal length of the first lens group, F ₃ is the focal length of the third lens group, h ₁ is the beam diameter of the substantially parallel light beam on the first lens group side of the second lens group, and h ₃ is the second It is a light beam diameter of a substantially parallel light beam on the third lens group side of the lens group.

When (F ₁ × h ₃ ) / (F ₃ × h ₁ ) is 0.3 or more, the light beam height cannot be reduced by increasing the focal length F ₁ of the first lens group. On the other hand, shortening the focal length F ₃ of the third lens group can not be increased the ray height at the third lens group, it is impossible to correct the aberrations in the third lens group. When (F ₁ × h ₃ ) / (F ₃ × h ₁ ) is 0.2 or less, the focal length F ₁ of the first lens group is shortened, making it difficult to correct spherical aberration.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (2) and (3).
(2) 0.25 <(D ₁ × NA) / (R ₁ × n ₁ ) <0.35
(3) 1.5 <d ₁ / D ₁ <2.5
However, D ₁ is the smallest lens diameter in the first lens group, NA is the object side numerical aperture of the small-diameter objective optical system, R ₁ is the smallest radius of curvature in the first lens group, n ₁ is the first lens group The largest refractive index, d _1, is the distance from the object plane to the image plane of the lens closest to the image plane in the first lens group.

When (D ₁ × NA) / (R ₁ × n ₁ ) is 0.35 or more, the lens outer diameter D ₁ becomes large, and a thin objective optical system cannot be formed. In order to reduce the lens diameter D ₁ is not necessary to reduce the radius of curvature R _1, the radius of curvature R ₁ becomes the refractive power is strong becomes spherical aberration of the first lens group becomes insufficient correction small. When (D ₁ × NA) / (R ₁ × n ₁ ) is 0.25 or less, the object surface side numerical aperture NA becomes small, or the curvature radius R ₁ becomes large, so that spherical aberration is overcorrected. A malfunction occurs.

When d ₁ / D ₁ is 2.5 or more, the distance d ₁ from the object plane to the image plane of the lens closest to the image plane in the first lens group is large, and the amount of spherical aberration generated is small. Ray height will be high. When d ₁ / D ₁ is 1.5 or less, d ₁ becomes small, so divergent light must be converted into substantially parallel light at a short distance, and the amount of generation of spherical aberration and coma increases.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (4), (5), (6).
(4) 10 <| ν ₃₁ −ν ₃₂ |
(5) 0.12 <| n ₃₁ −n ₃₂ | <0.2
(6) 4 <F ₃ / R ₃ <5.5
Where ν ₃₁ is the Abbe number for the d-line of a lens having a large Abbe number among the cemented lenses of the third lens group, and ν ₃₂ is the Abbe number for the d-line of a lens having a small Abbe number among the cemented lenses of the third lens group, n ₃₁ is a refractive index for the d-line of a lens having a large Abbe number among the cemented lenses of the third lens group, n ₃₂ is a refractive index for a d-line of a lens having a small Abbe number among the cemented lenses of the third lens group, and F ₃ the focal length of the third lens group, and R ₃ is the radius of curvature of the cemented surface of the cemented lens in the third lens group.

If | ν ₃₁ −ν ₃₂ | is 10 or less, the difference in Abbe number in the cemented lens becomes small, and correction of chromatic aberration becomes difficult.

When | n ₃₁ −n ₃₂ | is 0.12 or less, the radius of curvature of the cemented surface becomes small and lens processing becomes difficult. When | n ₃₁ −n ₃₂ | is 0.2 or more, the radius of curvature of the joint surface becomes large, and it becomes difficult to correct spherical aberration and coma aberration.

When F ₃ / R ₃ is 4 or less, the focal length F ₃ of the third lens group becomes small, and the ray height in the third lens group cannot be reduced. Alternatively, the curvature of the cemented surface of the cemented lens in the third lens group R ₃ is increased, a problem can not be corrected aberrations generated in the first and second lens group is generated. When F ₃ / R ₃ is 5.5 or more, the curvature radius R ₃ of the cemented surface of the cemented lens of the third lens group becomes small, resulting in inconvenience that spherical aberration and coma aberration are overcorrected.

  According to the present invention, living tissue of mammalian cells including small experimental animals, muscles and other biological tissues, or various organs such as the heart and liver, particularly brain tissues, remain alive for a relatively long period of time. It becomes possible to observe.

Hereinafter, an embodiment of a small-diameter objective optical system of the present invention will be described with reference to FIG.
The small-diameter objective optical system 1 according to this embodiment includes a first lens group G ₁ , a second lens group G _2, and a third lens group G _{3 in} order from the object plane side.

The first lens group G ₁ has a plano-convex lens L ₁ having a convex surface directed toward the image side, and a plano-convex lens L ₂ with a convex surface facing the object side. The first lens group G ₁ is a positive refractive power as a whole.

The second lens group G ₂ is aimed cemented lens of a plano-convex lens L ₄ with the convex surface facing the concave lens L ₃ and the object plane side having a concave surface directed toward the image side, a concave surface on the object side concave A cemented lens in which a flat lens L ₅ and a plano-convex lens L ₆ having a convex surface facing the image surface are cemented, a plano-convex lens L ₇ having a convex surface facing the image surface, and a concave flat lens L ₈ having a concave surface facing the object surface It is composed of bets bonded cemented lens, and a plano-convex lens L ₉ with the convex surface facing the image side.

The third lens group G ₃ includes a cemented lens having a negative refractive power and a convex-plano lens L ₁₁ having a convex surface on the plano-concave lens L ₁₀ and the object plane side having a concave surface directed toward the image side, a convex surface on the object side A convex flat lens L ₁₂ facing, a cemented lens of a plano-convex lens L ₁₃ having a convex surface facing the image surface and a concave flat lens L ₁₄ having a concave surface facing the object surface, and a convex flat having the convex surface facing the object surface. It is composed of a lens _{L 15.}

In small-diameter objective optical system of FIG. 1, the focal length of the third lens group G ₃ is larger than the focal length of the first lens group G _1.

In the present embodiment, each lens is configured to satisfy the following conditional expressions (1) to (6).
(1) 0.2 <(F ₁ × h ₃ ) / (F ₃ × h ₁ ) <0.3
(2) 0.25 <(D ₁ × NA) / (R ₁ × n ₁ ) <0.35
(3) 1.5 <d ₁ / D ₁ <2.5
(4) 10 <| ν ₃₁ −ν ₃₂ |
(5) 0.12 <| n ₃₁ −n ₃₂ | <0.2
(6) 4 <F ₃ / R ₃ <5.5

Here, F ₁ is a focal length of the first lens group G ₁ , F ₃ is a focal length of the third lens group G ₃ , and h ₁ is a light beam of a substantially parallel light beam on the first lens group side of the second lens group G ₂ . The diameter, h ₃ is the diameter of the substantially parallel light beam on the third lens group side of the second lens group G ₂ , D ₁ is the smallest lens outer diameter in the first lens group G ₁ , and NA is the object of the small objective optical system side numerical aperture, R ₁ is the first lens group G ₁ in the smallest radius of curvature, n ₁ is the largest refractive index in the first lens group G _1, d ₁ is the most in the first lens group G ₁ from the object plane the distance to the image plane of the lens on the image side, [nu ₃₁ is the Abbe number at the d-line of the lens having a large Abbe number in the cemented lens of the third lens group G _3, [nu ₃₂ is bonded to the third lens group G ₃ Abbe number of d line of the small lenses of the Abbe numbers of the lenses, n ₃₁ and the third lens group G Refractive index at the d-line of lens having a large Abbe number in the cemented lens of, n ₃₂ is the refractive index at the d-line of the small lenses of the Abbe numbers in the cemented lens of the third lens group G _3, R ₃ denotes a third lens unit curvature of the cemented surface of the cemented lens G ₃ is the radius.

The first lens group G ₁ is capable of nearly image-side convex surface of the plano-convex lens L ₁ to the aplanatic condition, which makes it possible to reduce the amount of generation of the spherical aberration and coma aberration. Further, when the focal length of the entire first lens group is shortened, the amount of spherical aberration and coma aberration generated in the entire first lens group becomes relatively large, but the divergent light beam from the object surface is not increased without increasing the ray height. substantially it can be converted into divergent light beam close to a parallel light flux or substantially collimated light, and guide the light fluxes obtained second lens group G _2.

The second lens group G ₂ is a divergent light beam close to a substantially parallel light beam or a substantially parallel light from the first lens group further expanded to larger substantially parallel beam of diameter, are led to light in the third lens group.

The third lens group G _3, by including a cemented lens having a cemented surface of negative refractive power, monochromatic aberration and the chromatic aberration correction, including spherical aberration and coma aberrations generated in the first and second lens group ing.
Also, by increasing the ray height by increasing the focal length F ₃ of the third lens group than the focal length F ₁ of the first lens group G _1.

FIG. 2 is a lens arrangement diagram in which the relay optical system 2 is arranged on the image plane side of the small-diameter objective optical system 1 in FIG. 1 and the emitted light beam from the object is made parallel light. FIG. 3 shows an example of a lens configuration diagram of the relay optical system 2, and Table 1 shows an example of lens data of the relay optical system 2. 3 and Table 1, the Abbe Number of symbols r is the radius of curvature, the sign d is the axial distance, refractive index at reference numeral _{n d} is the d-line (587.56 nm), the code [nu _d is the d-line (587.56 nm) Indicates.

  With the configuration as shown in FIG. 2, the small-diameter objective optical system 1 according to this embodiment can be compatible with a microscope system designed at infinity. At this time, the objective optical system of the present invention can be inserted into a deeper part of the living body with minimal invasiveness by designing the relay optical system 2 so that the beam diameter on the small objective optical system side becomes small. it can.

  When the relay optical system 2 is arranged on the image plane side of the small-diameter objective optical system 1 as shown in FIG. 2, the light emitted to the image plane side of the relay optical system 2 becomes parallel light and no image is formed. Therefore, for example, an imaging lens 3 (focal length 180) having the lens data of Table 2 as shown in FIG. 4 is arranged on the image plane side of the relay optical system 2 to form an image.

Example 1
Example 1 of the present invention will be described using the small-diameter objective optical system shown in FIG.
Table 3 shows lens data of the small-diameter objective optical system in FIG. FIG. 5 shows aberration diagrams of the thin objective optical system shown in FIG. In FIG. 5, the symbol NA indicates the numerical aperture on the object plane side, and the symbol Y indicates the object height.

In the small-diameter objective optical system 1 according to Example 1, the lens diameters from L _{1 to} L ₄ are 0.46 mm, the lens diameters from L _{5 to} L ₈ are 0.6 mm, and the lens diameters from L _{9 to} L ₁₅ Is 0.82 mm, and is constituted only by a lens having a very small diameter.
For this reason, the small-diameter objective optical system 1 according to the present embodiment is suitable for in vivo observation of a deep inside body of a small experimental animal such as a mouse for a relatively long period of time with minimal invasiveness.

(Example 2)
FIG. 6 shows a lens configuration diagram of Example 2 of the small-diameter objective optical system according to the present invention. The thin objective optical system 10 according to the second embodiment has a longer working distance WD than the first embodiment. As a result, the lens tip is prevented from touching the observation target, and observation can be performed with as little physical influence as possible on the living body.
Table 4 shows lens data of the small-diameter objective optical system shown in FIG. FIG. 7 shows aberration diagrams of the small-diameter objective optical system shown in FIG. 6 and 7 and Table 4 are the same as those in the first embodiment.

In the small-diameter objective optical system 10 according to the present embodiment, the lens diameters from L _{1 to} L ₄ are 0.46 mm, the lens diameters from L _{5 to} L ₉ are 0.6 mm, and lenses from L _{10 to} L ₁₆ are used. The diameter is 0.8 mm, and it is composed only of a very small lens.
For this reason, the small-diameter objective optical system 10 of the present embodiment remains alive in mammalian cells including small experimental animals, biological tissues such as muscles, or various organs such as the heart and liver, particularly brain tissues. It is suitable for in vivo observation with minimal invasiveness over a relatively long period of time.

  Table 5 shows data of conditional expressions (1) to (6) in the first and second embodiments.

  The small-diameter objective optical system of the present invention has good aberrations up to the near infrared region. Therefore, not only the skin of the sample but also the inside of the living body can be observed with relatively small scattering using near infrared light. It can also be used for a multiphoton excitation observation apparatus.

It is a lens block diagram of the small diameter objective optical system which concerns on this invention. FIG. 2 is a lens layout diagram in which an infinitely designed relay optical system is arranged on the image side of the small-diameter objective optical system in FIG. It is a lens block diagram of the relay optical system of FIG. FIG. 3 is a lens cross-sectional view showing an example of an imaging lens arranged on the image side of the relay optical system of infinity design in FIG. 2. FIG. 4 is an aberration diagram of the small-diameter objective optical system of Example 1; (a) spherical aberration, (b) sine condition violation amount, (c) astigmatism, and (d) distortion aberration. It is a lens block diagram which concerns on the 2nd Example of a small diameter objective optical system. FIG. 6 is aberration diagrams of the small-diameter objective optical system of Example 2, and shows (a) spherical aberration, (b) sine condition violation amount, (c) astigmatism, and (d) distortion aberration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Small-diameter objective optical system 2 Relay optical system 3 Imaging lens G ₁ 1st lens group G ₂ 2nd lens group G ₃ 3rd lens group

Claims (4)

  In order from the object surface side, a first lens unit having positive refractive power including at least one plano-convex lens having a convex surface directed toward the image surface side, a second lens group having positive refractive power including at least one concave lens, and a cemented surface Is composed of a third lens group including a cemented lens having a negative refractive power, and the focal length of the third lens group is larger than the focal length of the first lens group. 2. The small-diameter objective optical system according to claim 1, wherein the following conditional expression (1) is satisfied.
(1) 0.2 <(F ₁ × h ₃ ) / (F ₃ × h ₁ ) <0.3
However,
F ₁ : focal length of the first lens group G ₁
F ₃ : focal length of the third lens group G ₃
h ₁ : a beam diameter of a substantially parallel light beam on the first lens group side of the second lens group G ₂ ;
h ₃ is a beam diameter of a substantially parallel light beam on the third lens group side of the second lens group G ₂ . The small-diameter objective optical system according to claim 1 or 2, wherein the following conditional expressions (2) and (3) are satisfied.
(2) 0.25 <(D ₁ × NA) / (R ₁ × n ₁ ) <0.35
(3) 1.5 <d ₁ / D ₁ <2.5
However,
D ₁ : the smallest lens outer diameter in the first lens group G ₁ ,
NA: numerical aperture on the object plane side of the small-diameter objective optical system,
R ₁ : the smallest radius of curvature in the first lens group G ₁
n ₁ : The largest refractive index in the first lens group G ₁ ,
d ₁ : Distance from the object plane to the image plane of the lens closest to the image plane in the first lens group G ₁ . The small-diameter objective optical system according to any one of claims 1 to 3, wherein the following conditional expressions (4), (5), and (6) are satisfied.
(4) 10 <| ν ₃₁ −ν ₃₂ |
(5) 0.12 <| n ₃₁ −n ₃₂ | <0.2
(6) 4 <F ₃ / R ₃ <5.5
However,
ν ₃₁ : Abbe number for the d-line of a lens having a large Abbe number among the cemented lenses in the third lens group G ₃ ,
ν ₃₂ : Abbe number for the d-line of a lens having a small Abbe number among the cemented lenses in the third lens group G ₃ ,
n ₃₁ : refractive index with respect to d-line of a lens having a large Abbe number among the cemented lenses of the third lens group G ₃ ;
n ₃₂ : refractive index with respect to d line of a lens having a small Abbe number among the cemented lenses of the third lens group G ₃
F ₃ : focal length of the third lens group G ₃
R ₃ is the radius of curvature of the cemented surface of the cemented lens of the third lens group G ₃ .

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